Wednesday, April 8, 2009

Italy's Earthquake

This week's tragic earthquake in Italy is just another reminder that Earth's evolution continues to unfold and that human populations, especially those near active plate margins, remain at risk. Our brief life span, but a fleeting moment in geologic time, often gives us the impression that this planet has settled into a stable, mature state; then, another natural catastrophe forces us to face reality.

When the Tethys Sea split Pangea, 200 million years ago, the land that is now Italy moved south as part of the African Plate. As the Sea closed, the African and Eurasian Plates began to collide and Italy became the leading edge of that collision. Forced against southern Europe like a giant wedge, the Italian terrain was reunited with Eurasia and the impact of that collision rippled up the Alps and adjacent ranges. Beginning 50 million years ago, the process continues today, producing a vast network of faults throughout the region, all of which are subject to the type of motion that caused this week's earthquake.

Wherever tectonic plates collide, subduct or scrape against one another, the potential for a powerful earthquake exists. The best we can do is to design our structures in such a way that they withstand mild to moderate quakes and avoid development in areas where faults are relatively shallow (i.e. near the surface). But any powerful earthquake in an urbanized area is almost certain to be catastrophic and, as history has demonstrated, many more are sure to follow.